The present invention relates, in general, to electronic sensor packages and, more particularly, to pressure sensor packages for reducing stress-induced measurement error.
A gasoline tank rollover valve containing a pressure sensor will likely be required in a few years for all cars and light trucks produced for sale in the United States. Prior pressure sensor packages have been attached to liquid fuel tanks either to a mounting assembly on the tank itself or to an assembly at a remote location of the vehicle with a pressure-transmitting tube connecting the fuel tank to the pressure sensor. However, in both cases, these prior pressure sensors have suffered from stress-induced measurement errors due to the need to mount the pressure sensor to a portion of the vehicle. Examples of such stress include vehicle vibration and thermal expansion due to temperature changes.
Because a pressure sensor typically incorporates a sensitive thin silicon membrane disposed on a semiconductor die, vibration and thermal expansion that are transmitted through sensor mounting hardware, both from the hardware itself and the vehicle it is mounted on, contribute to pressure measurement error. Accordingly, there is a need for a pressure sensor that reduces stress-related measurement errors from vehicle vibration, thermal variations, and other related factors in order to accurately determine the pressure of the vapor in an automobile's fuel tank.